This application is based on application No. 2000-127213 filed in Japan, the content of which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to an image display apparatus that is used in front of a user""s face and that provides images that are superimposed over external images.
2. Description of the Prior Art
As information-providing means for personal use, image display apparatuses have been proposed that are mounted in front of a user""s face and lead light from a displayed image to the user""s eye together with external light so that the displayed image is superimposed over external images. A user can use such an apparatus in a variety of everyday situations, such as observing displayed images while walking.
An apparatus of this kind generally has the configuration of glasses having a frame, a pair of lenses, nose pads and a pair of temples The display device that displays images is housed in a container mounted around the frame. In order for the displayed image to be superimposed on external images, light from the display device, which is located at the side, must be led to a location immediately in front of the eye and the light path must be changed there such that the light strikes the eye from the front. It is also preferred that the images displayed in a small display device be enlarged for observation. For this purpose, a hologram element is used.
For example, Japanese Laid-Open Patent Application Hei 11-64781 discloses an apparatus having a hologram element on a front surface of a lens (i.e., a surface located farther away from the eye). Light from a display device is led into the lens from an edge area of the lens, directly striking the hologram element, and after it is diffracted, it is led to the eye. On the other hand, Japanese Laid-Open Patent Application Hei 11-64782 discloses an apparatus having a hologram element on a rear surface of a lens (i.e., a surface closer to the eye). Here, light from a display device is led to the hologram element from the rear surface of the lens, where it is diffracted without striking the lens and led to the eye.
In these examples, a user observes actual external images together with an enlarged virtual image of the displayed image. However, a part of the external light is blocked by a container or a frame such that an eclipse occurs in the field of view.
The fact that external light is blocked by a container or a frame does not pose a problem for the purpose of providing displayed images. Nevertheless, for safety purposes, as large a field of view as possible must be maintained by reducing the range over which the light is blocked by a container or a frame since the apparatus may be used in a variety of everyday situations.
However, in conventional apparatuses, containers and frames are designed with a principal focus on ease of arrangement of the optical system or increased strength of the apparatus, and their sizes and configurations are not suitable for the purpose of ensuring a large field of view.
An object of the present invention is to overcome these and other shortcomings in the prior art designs.
Another object of the present invention is to provide an improved image display apparatus.
Another object of the present invention is to provide an image display apparatus in which the range of the field of view blocked by the container for housing the display device or blocked by the frame is small.
These objects are attained by an image display apparatus comprising nose pads that come into contact with a user""s nose and a pair of temples that come into contact with a user""s ears, sides of head, or rear area of head. The image display apparatus is worn in front of a user""s face, such that (i) the apparatus leads light from a displayed image to a user""s eye together with external light so that the displayed image is superimposed on external images, (ii) wherein the apparatus includes one or two display units including a display device that displays images, a container that supports the display device, and an eyepiece optical system that leads the light from the display device to the eye and provides a virtual image of the displayed image, and (iii) wherein at least one length of the container that extends in a direction perpendicular to a direction connecting the container and the eye is shorter than the length of the container that extends in the direction connecting the container and the eye.
The display device provides displayed images to at least one eye, and depending on whether one or two display devices are included, the image display apparatus may be an apparatus for one-eyed observation or two-eyed observation. The configuration of the container is such that it is thin in the direction perpendicular to the line of sight when the user looks toward the container. Therefore, the range of field of view that is blocked by the container is small. At the same time, because the container is long in the direction along the above line of view, even when a light source and optical system to illuminate the display device are included in the container, they can be easily arranged therein.
Here, the container should support the display device such that the display surface thereof is essentially perpendicular to the direction connecting the center thereof to the eye. In this way, when a transmission-type display device, which allows the illuminating light to pass through, is used for the display device, the illuminating light source and optical system may be placed along an extension of the straight line connecting the eye and the center of the display surface, so that the light source and optical system may have simple and lightweight constructions without increasing the width of the container.
The above objects are further attained by an image display apparatus comprising nose pads that come into contact with a user""s nose and a pair of temples that come into contact with a user""s ears, sides of head, or rear area of head. The image display apparatus is worn in front of a user""s face, wherein (i) the apparatus leads light from a displayed image to a user""s eye together with external light such that the displayed image is superimposed on external images, (ii) the apparatus includes one or two display units including a display device that displays images, a container that supports the display device, and an eyepiece optical system that leads light from the display device to the eye and provides a virtual image of the displayed image, and (iii) the container is configured such that an angle over which a user""s field of view is blocked is determined by a part of the container closer than the center thereof to the eye in a direction connecting the container and the eye.
When the container has this configuration, a range of the blocked field of view may be reduced relative to a different configuration, and the container itself may be reduced in size, making the apparatus more lightweight. For example, if the angle over which the field of view is blocked is determined by a part of the container that is closer than the center thereof to the eye and a part of the container that is farther than the center thereof away from the eye, the range of the blocked field of view increases; if the angle over which the field of view is blocked is determined by a part of the container that is farther than the center thereof away from the eyes, the container increases in size.
A prism may be included in each of the above image display apparatuses, wherein such prism is located in front of the eye, allows external light pass through, and leads the external light to the eye; a part thereof also operates as an eyepiece optical system that leads light from the display device to the eye.
When at least a part of the eyepiece optical system is located in the field of view, it may affect the external light that passes therethrough in some way and may cause distortion or discontinuity in external images provided to the user. By including a prism that also operates as an eyepiece optical system, so that the prism has the same effect as an eyepiece optical system with regard to the external light that does not pass through an eyepiece optical system, or so that the effect of an eyepiece optical system is offset by the prism, the occurrence of distortion and discontinuity in the external images may be avoided. In addition, by mounting the container, nose pads, and temples to the prisms, a connecting member such as a frame to integrate these members may no longer be needed.
The above objects are also attained by an image display apparatus comprising nose pads that come into contact with a user""s nose and a pair of temples that come into contact with a user""s ears, sides of head, or rear area of head. The image display apparatus is worn in front of a user""s face, wherein (i) the apparatus leads light of a displayed image to a user""s eye together with external light such that the displayed image is superimposed on external images, (ii) the apparatus includes one or two display units including a display device that displays images, a container that supports the display device, and an eyepiece optical system that leads light from the display device to the eye and provides a virtual image of the displayed image, and (iii) because the prisms are mounted to the nose pad assembly and the temples and the container or containers are mounted to the prisms, a connecting member such as a frame to integrate the container or containers, nose pad assembly and temples is not needed.
In this apparatus, a connecting member such as a frame to integrate the container, nose pads and temples is not needed, such that the field of view is not blocked by a connecting member.
A part of each prism of this apparatus should also operate as an eyepiece optical system such that light from the display device is led to the eye. In doing so, as described above, the occurrence of distortion and discontinuity in external images may be avoided.
In the image display apparatus having the above prisms, the container or containers are located around the prism or prisms and each prism may have a construction in which it has, as an eyepiece optical system, a surface that leads light from the display device to the interior of the prism, a surface that reflects several times inside the prism the light thus led to the interior of the prism and leads it close to the eye, and a surface that directs the light led to a location immediately in front of the eye toward the eye. Because light from the display device is reflected inside the prism and is led to a location immediately in front of the eye, the container may be located around or outside of the field of view, resulting in a larger field of view. In addition, the prism may be made thinner.
The surface that directs the light led to a location immediately in front of the eye should comprise a hologram element. In doing so, the prism can lead both the light from the display device and the external light to the eye without light loss, and the display image or external images superimposed on the display image do not become dark, even while the apparatus maintains a simple construction.
The prisms should have magnification powers by which to correct a diopter. In this way, a user with weak vision can also clearly observe the external world without using other correcting means.